The world energy crisis has greatly stimulated a demand for solid fuel products, both natural and artificial. A variety of artificial fireplace logs have been introduced to the marketplace along with various igniting and kindling devices and materials. Solid fuel components in the prior art are made from a wide range of materials including paper, certain waste vegetable fibers and common sawdust and/or wood chips or shavings compounded with some form of adhesive binder prior to compressing the material into a simulated fireplace log or the like.
Prior art solid fuel elements made from common sawdust contain bound moisture in the wood cell structure as well as free moisture absorbed from the ambient atmosphere. Such prior art fuel products which employ some form of wax for ignition purposes utilize the wax merely as a coating on the wood particles and/or as a binder, usually with certain adhesive additives, such as starches. This is both costly and wasteful. The wood particles in the prior art products lack the ability to become saturated with wax because of retained moisture.
Therefore, the objective of this invention is to deal with and overcome the above and other deficiencies of the prior art by the provision of a greatly improved solid fuel product, particularly suitable for use as a solid igniter for fireplace logs and packaged artificial fuels, and also capable of a wider utility in the solid fuel field.
This invention recognizes and takes advantage of the fact that in certain compressed wood products made from kiln dried lumber chips and shavings bound mositure in the wood cells is reduced substantially to zero in the processing of the product. This is due to the high degree of compression employed, commonly about 55,000 psi. The subsequent increase in temperature and resulting molecular activity releases and drives out bound moisture from the wood cells as vapor or steam.
Under the unique process of this invention, a waste or by-product of compressed wood articles in the form of fine sawdust is utilized exclusively along with a certain refined liquid wax at a critical elevated temperature which assures the release of any free moisture which may have entered the wood particles from the ambient atmosphere in the interim. The hot wax elevates the temperature of the compressed wood particles to substantially the same temperature which existed during formation of the parent compressed wood product, and this again produces molecular activity and separation to create voids which become filled with the wax, as there is now a complete absence of both bound and free moisture in the wood particles and they are highly absorbent and are able to become fully saturated with the wax during the blending phase of the process, to be fully described.
The ultimate product of the invention is superior in many respects to the known prior art. For example, a 1.times. 1-3/4 inches cylindrical igniter processed according to the invention has 20% of the burning time embodied in some prior art common sawdust artificial logs measuring 4 inches in diameter by about 141/2 inches long. The wood particles forming such prior art fuel elements are merely coated with wax or other petroleum derivative and are not saturated as with the invention and cannot become saturated because of the bound moisture retention of common sawdust.
With regard to the prior art, since the specific gravity of water is greater than the specific gravity of wax, the water or moisture can act only as a carrying agent or dispersant. A comparable example is the wax base water soluble oil in lapidary processes.
The product of the invention is not only completely moisture-free but also moisture repellent. It will float in water and can be submerged for a lengthy period of time and, upon removal from the water, will still ignite quite readily. Additionally, the product of the invention meets the Federal Clean Air standards whereas broadly comparable products in the prior art do not due to the presence of such contaminants as sodium nitrate, copper sulphate and other toxic materials.
According to another aspect of the invention process, the hot blended material is subjected to controlled cooling from two conditioned air sources while gradually passing through a cooling tower on a multi-level conveyor which delivers the cooled material into a cold air stream near the bottom of the tower by means of which the material is air-borne for a time before gravitating into a collector chamber from which the cooled material is delivered to a storage bin, prior to passing through a hammer mill which imparts final uniformity to the material immediately prior to compression into the final product.
The final processing step is compression or compacting of the material into a solid igniter element or larger solid fuel component, in some cases. During the compression operation, additional fine compressed wood sawdust is employed as a release agent which allows easy separation of the product from the compression chamber or cylinder, without clogging, sticking or building up of material on the bottom of the compactor shaft. The use of this dry sawdust release agent avoids the necessity for constant cleaning of parts by absorbing the slight amount of melt at the ends of the solid igniter elements being formed under extreme pressure of approximately 22,000 psi. The release agent feature is important and critical to the success of the process in terms of commercial volume and automation.
Other features and advantages of the invention will appear during the course of the following detailed description.